Heretofore the principal types of exhaust ducting or stacking used in repair shops for motor vehicles and especially for diesel engines have been formed of relatively light sheet metal or other such material with flexible tubular elbows or other sections to permit the inlet end of the stacking to be moved onto the exhaust pipe of the engine. Some degree of movability is required of the inlet of such stacking because of the varying positions of the engine when vehicles are driven into the work positions. A principal deficiency of the former stacking is that the intense heat of the engine exhausts very soon destroys the stacking, particularly in the elbows or curved parts, which are subjected to the inertia of the gases at very high temperatures, in order the deflect them, and which are inherently weakened by being required to flex.
Where heretofore there have been telescopic stacking, it has usually been of very limited movability.